This is normal
Probably normal: defrost mode
Heat pumps pause heating to melt frost off the outdoor coil. The fan stops, you may see steam, and indoor air runs cool for a short time.
Why this happens
Carrier says light frost that melts during defrost mode is normal. In cold, damp weather, frost builds on the outdoor coil, and the heat pump briefly reverses to melt it. Trane says once it exits defrost mode, it should resume heating as normal.
What to do
- Wait. Defrost ends on its own and heating resumes.
- If snow or debris is piled against the outdoor unit, set the thermostat to Off and switch off the outdoor disconnect before you clear it by hand, then switch both back on.
- Don't chip at the frost or pour water on the unit.
- If the outdoor unit stays coated in ice, or the air never warms up again, come back and choose that answer.
If it still worries you, tell the HVAC technician
- How often defrost happens and how long it lasts.
- Whether ice ever fully clears from the outdoor unit.
- The outdoor temperature when you saw it.
Build the full list: what to tell the HVAC technician.
Start this troubleshooter over
References (every fact above comes from one of these pages)
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